Probing the Kinetics and Thermodynamics of Copper(II) Binding to<i>Bacillus subtilis</i>Sco, a Protein Involved in the Assembly of the Cu<sub>A</sub>Center of Cytochrome<i>c</i>Oxidase
Bibliographic record
Abstract
BsSco is a member of the Sco protein family involved in the assembly of the Cu(A) center within cytochrome c oxidase. BsSco forms a complex with Cu(II) that has properties consistent with dithiolate ligation. Stopped-flow UV-visible absorbance and fluorescence coupled with multiwavelength analysis reveal biphasic binding kinetics between BsSco and Cu(II). An initial species appears with absorbance centered at 382 nm at a copper concentration-dependent rate (2.9 x 10(4) M(-1) s(-1)). The initial species decays at a first-order rate (1.5 s(-1)) to the equilibrium form with a maximum at 352 nm. Formation of the BsSco-Cu(II) complex is accompanied by quenching of protein fluorescence. The copper concentration-dependent phase gives 70% of the total quenching, while the final 30% develops during the second phase of the absorbance change. The pH dependence of copper binding shows that the copper-dependent rate increases by 50-fold as the pH decreases from 8.5 to 5.5 with an apparent pK(a) of 6.7. The slower phase rate is independent of pH. Comparison of circular dichroism spectra between apo-BsSco and the BsSco-Cu(II) complex reveals a small change in the UV region consistent with a subtle conformational change upon copper binding. There is formation of a distinctive visible CD spectrum in the BsSco-Cu(II) complex. A model is presented in which the kinetic and thermodynamic stability of the BsSco-Cu(II) complex results from a two-step mechanism. Release of copper would be facilitated in the intermediate form of BsSco, and attaining such a low-Cu(II) affinity state may be important for BsSco's function in Cu(A) assembly.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".